1. Field of the Invention
The present invention relates to a bearing device for supporting a shaft by providing a plurality of projections on either the bearing or the shaft.
2. Background Prior Art
Generally, a bearing device rotatably supports a shaft in a bearing. Recently, bearing devices having a plurality of radial projections formed on either the inside peripheral surface of the bearing or the peripheral surface of the shaft have been proposed. The devices proposed have, for example, a structure as shown in FIG. 4. The bearing device illustrated in FIG. 4, which employs a so-called three-point supporting bearing, has 3 radial projections 1b formed on the inside peripheral surface of a bearing 1 formed of an oil impregnated sintered metal. Between each projection 1b and a mating shaft 2 facing to the projections 1b, a wedge-shaped oil film 3 is produced, respectively, to create so-called self-lubrication.
However, since the projections 1b in the conventional bearing device have the portions facing to the mating part formed to a linear shape, the dynamic pressure effect of the oil film 3 is very small. Accordingly, when a large load is applied to the shaft 2 in an eccentric direction, the projections 1b of bearing 1 may make metal-to-metal contact with the shaft 2, which causes wear of projections 1b. As the wear progresses, the projections gradually become small, and a normal oil film cannot be formed.
A primary object of the present invention is to provide a bearing device which increases the resistance to wear of the projections for supporting the shaft.